Draft control



April 22, 1952 w. B. STEPHENSON 2,593,808

DRAFT CONTROL Filed Jan. 14, 1948 2 SHEETSSI-IEET 1 INVENTOR. WiLLBAifi B, STEPHENSON M MM. wry

ATT'YS AprilE 22, 1952 w. B. STEPHENSON 2,593,808

DRAFT CONTROL Filed Jan. 14, 1948 2 SHEETSSHEET 2 n HHHIIHHI" 0 0|- -fiq HM I l.

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Patented Apr.. 22, 1952 I UNITED v. STATE s PATENT OFFICE 7 2,593,808 DRAFT CONTROL William B. Stephenson, Fond du Lac, Wis. Application January 14, 1948, Serial No.--2,241 2 Claims. (01. ass-45) The invention relates generally to improvements in draft controls, and more particularly to controls for automatically admitting air to a furnace stack to regulate the draft.

The general object of the invention is to provide a novel draft control which will completely close the draft opening in the event of a sudden pressure increase in the combustion chamber.

More specifically, it is an object toprovide a novel draft control utilizing a damper plate which is pivoted within a frame for movement under the influence of the draft about a generally horizontal axis so located that the plate will open inwardly at the top, and the upper and lower portions of which at opposite sides of the axis are laterally offset with respect to each other so that when the plate is closed, the lower portion will engage the outside of the frame.

Other objects and advantages will become apparent as the description proceeds.

In the accompanying drawings,

Figure 1 is a perspective view of a draft'con trol embodying the features of the invention.

Fig. 2 is a side elevational view, partially in axial section, of the draft control shown in Fig. l.

Fig. 3 is a front view of a modified form of the draft control.

Fig. 4 is a fragmentary side elevational view of the draft control shown in Fig. 3.

' As shown in the drawings, the draft control constituting the'preferred form of the invention comprises a duct l adapated to be attached to and extend laterally of a stack or flue l l leading from a furnace (not shown) to a chimney (not shown). The duct I0 is adapted to be placed endwise over a hole (not shown) in one side of the stack, the rear end of the duct being cut on the curvature of the stack, as shown at I2, so that it will fit closely against the stack. To clamp the duct rigidly in place, means such as a pair of straps or hands I3 is provided. Each band has one end secured to the ductby extending through a slot therein and being reversely bent, as at [4. The two bands embrace the stack; II, and their free ends are connected by-being bent to extend laterally from the stack in faceto-fa-ce relation with each other for connection, as by a nut and bolt I5.

A damper plate 20 is located in the outer end of the duct l0, and is pivotally supported so that it may swing to permit air to enter the stack through the duct. Since the air entering the stack, if permitted to enter the top thereof, creates less turbulence within the stack, and consequently provides for more accurate control of I the air through the fire, the damper plate 20 is pivoted on a horizontal axis in such a manner that in the opening movement the top of the plate will move inwardly of the duct. The position of the stack may differ in different installation, that is, the stack may be located horizontally or vertically, or at an angle. It is, therefore, desirable to provide a pivotal support for the damper plate 20 which may be adjusted to bring the pivotal axis in a substantially horizontal position for any. position of the stack. To this end, the damper plate 20 is supported by the annular mounting frame 2! telescoping within the outer end of the duct Ill, and rotatably adjustable therein. Any

simple pivoting means may be provided for the plate 20, the particular one herein shown com-- prising a pair of lug members 22 secured to the plate 20 and supported on a shaft 23 extending through the annular frame 2 l.

To permit the damper plate 20 to swing inwardly of the duct ID at the top, the pivotal axis of the plate is located below the vertical center thereof so that the area above the axis is greater than the area below the axis. If the damper plate 20 were exactly round and the diameter thereof were such as to fit snugly within the frame 2|. the plate when so mounted would bind or stick against the sides of the ductupon swinging out of closed position through an angle less than required. To prevent such binding and thereby permit the plate to swing freely through the required range of movement, the side edges of :the

plate are flattened as indicated at,24.,,or alternatively a-ss'mall clearance may lee-provided between the periphery of the plate and the interior 1 of the frame 2 l.

The damper plate 20 is preferably made of sheet metal and, since the pivotal axis thereof is below its horizontal center line,- counterbalancing means is attached to the lower part of the plate to prevent the weight of the plate from causing it to swing inwardly excessively, and to regulate the inward swinging movement in accordance with the draft. Preferably, the counterbalancing means extends outside of the duct and frame so that it is readily accessible, and is adjustable to suit the draft conditions in any installation.

In the form shown for exemplary purposes, the counterbalancin means comprises a U-shaped bracket 25 having its arms extending substantially perpendicular to the plane of the damper plate. of its arms is bent laterally, as at 26, so that it may lie fiatwise against the outer face of the. damper. plate and be secured thereto, asbyscrews;

To attach the bracket 25 to the plate, one.

V 3 21. The other arm of the bracket, indicated at 30, extends generally parallel to and alongside the exterior of the duct I0, and carries and adjustable weight comprising a member 3| slidable on the arm 30 and a weighted clamping screw 32. As is clearly shown in drawings, the member 3| may be adjusted along the arm 30 and clamped in any desired position to suit the draft conditions in a particular installation. Thus, since the arm extends from a point beyond the outer end of the duct l0, toward the stack and alongside the duct, the weight may be shifted from a position to the right of the plane of the damper plate, as shown in various figures of the drawings, or may adjusted/to a position to the left of such plate should a high draft be desired.

In order to define'the closed position of the damper plate 20 the lower portion 33 is laterally oifset outwardly with respect to the upper portion 34. Preferably, the offset is located substantially at or closely adjacent the. axis of pivotal movement. Thus, lower and upper sections 33 and 34 are integrally connected by a transverse flange 35. The lug members 22 through which the shaft 23 extends may be conveniently welded to the upper section 34 with their curls disposed against the underside of the flange 35 as shown in Fig. 2. Byreason of the lateral offset defined by the flange 35. thelower plate section 33 is always located externally of. the frame 2|. This section is extended transaxially so that, when the. damper plate 20 is in closed position, the lower marginal edge portion thereof will overlap and flatly abut the lower marginal edge portion of the outer faceof the frame 2!. As a result, any sudden pressure increase in the combustion chamber transmitted through the breaching orduct l will tend to close the damper plate 26 and the latter will seal the opening to prevent the escape of obnoxious gases therethrough into the boiler room. a

The modified form of invention illustrated in Fig. 3 differs in one primary respect from that of Figs. 1 and 2 in that it is embodied in a foursided, rather than circular, structure. More particularly, the breaching I00. is square in crosssection, and is constructed of angle iron frame members at the edgesrigidly welded together to support suitable side-wall sheet metal panels 35 defining a flow passage. At the rear end of the breaching Inc, the angle irons define a frame 31 with outwardly projecting legs presenting a circumscribing mounting flange 38 adapted to be bolted to a stack 39. At the front end. of the breaching Illa, the angle irons define a frame 40 with inwardly projecting legs presenting an internal flange 4! circumscribing the air inlet opening. A damper plate 20a is mounted for pivotal movement within the frame 40. More particularly, the pivotal support comprises lug members 22a secured to the plate 20a, and supported on pins 23a journalled in the opposite vertical side member of the frame 2 i a.

The damper platellla is formed with an upper section 34a laterally offset inwardly with respect to the lower section 33a, and these sections are off-set transaxially approximately the thickness of the flange 4i so as to overlap and engagethe inner and outer faces of the flange when the plate 20a is in closed position. Thus, the lower section 330, is located externally of the frame 2 la and is adapted to engage the outer marginal edges of the flange 4|, and the upper section 34a is always locatedwithin the breaching Illa and is similarly.adaptedv to engage. the inner marginal edges of the flange when the plate 20a is moved into closed position. To this end, the damper plate 20a is made of a larger size than the air inlet opening, and is notched in the side edges, as indicated at 42, to receive the inner legs of the vertical angle irons adjacent the pivotal axis. Thus, the upper and lower sections of the plate 20a not only engage the frame 2m to define the closed position but, due to their overlap with the inwardly projecting legs ,of the frame 400., serve effectually to close the normal air inlet opening completely so as to prevent the escape of obnoxious gases into the boiler room.

Preferably, the pivot pins 23a define a pivotal axis located between the upper and lower edges but substantially below the horizontal center line of'theplate 20a, and the offset 35a between the upper'and lower plate sections 33a and 34a is located at or closely adjacent the pivotal axis 23a.

In this instance, the counterbalancing means, which may be of any suitable character, is duplicatedat opposite sides of the damper plate 20a. Preferably, each counterbalancing means comprises a lateral arm43 rigidly attached to the adjacent side of theplate 28asomewhat below the pivotal axis 230. and projecting therefrom laterally of the breaching Isa beyond the adjacent side of the frame 2 la. The outer end of the arm es is formed with a guide 44 through which a strap 45 is slidably extended. Theastrap 45 is adjustable in theguider44 transversely of the axis 23a and may be secured in position .of adjustment bymeans of a set screw 48; An arcuate tube 47v is rigidly attached at opposite ends in suspended relation to the ends. of the strap 45. A shiftable weight, in the form of a ball 48 is movably disposed in the tube 41.

It will be seen that, by reason of the foregoing construction, the counterbalancing means will influencethe action of the damper plate 20a to obtain the desired control of the draft. The in flux of air tends to swing the upper section 34a of the damper plate 25a inwardly. Outward movement of the damper plate 20a is limited by engagement thereof with the inwardly-projecting flange 4! of the frame member 2m to define a closed position in which the air inlet opening is completely sealed.

I claim as my invention:

l. A draft control comprising, in combination, a substantially horizontal rectangular duct, a rectangular frame-secured-in the inner end of said duct and separately-constructed of angle irons having outwardly extendinglegs defining a circumscribing flange adapted to be connected to a stack, a second rectangular frame secured in the outer end of said duct and defining an air inlet opening, said second frame bein separately constructed of angle irons having inwardly extending legs defining a flange in a common plane about said opening, a one-piece rectangular damper plate supported in said second frame for pivotal movement-about a generally horizontal axis and larger in dimensions'than said opening so as to overlap at its marginal edges with said last mentioned flange, said axis being located below and parallel to the horizontal center line of said second frame and damper plate and between the upper and lower edges of said plate and inwardly of the outer face of said second frame, the upper and lower portions of said plate respectively at opposite sides of the axis being bent into laterally offset relation with respect to each other by an amount substantially equal to-the thiekness-of-said angle iron legs to locate the upper portion inwardly of said last mentioned flange and the lower portion outwardly of said last mentioned flange, and being adapted to overlap and engage respectively the inner and outer margins of said last mentioned flange when said plate is in closed position, and adjustable counterbalancing means fixed on said lower portion of said plate and located entirely above the bottom edge of said plate, and comprising a weight adjustable into selected position tending either to maintain said plate in abutting engagement with said margins or to maintain said plate away from said margins in partiall open position.

2. A draft control comprising, in combination, a substantially horizontal rectangular duct adapted to be connected at one end to a stack, a rectangular frame secured in the outer end of said duct and defining an air inlet opening, said frame being separately constructed of angle irons having inwardly extending legs defining a flange in a common plane about said opening, a damper plate supported in said frame for pivotal movement about a generally horizontal axis, the upper and lower portions of said plate respectively at opposite sides of the axis being laterally ofiset with respect to each other by an amount substantiall equal to the thickness of said angle iron legs, whereby to locate the upper portion within said duct and the lower portion externally of said frame, said plate portions extending transaxially a sufficient distance to overlap and engage respectively the inner and outer margins of said flange when said plate is in closed position, and counterbalancing means mounted on opposite sides of the lower portion of said plate, each counterbalancing means having a laterally extending guide located adjacent said axis, a strap adjustable in said guide transversely of said axis and adapted to be extended to opposite sides of said axis, an arcuate tube connected at opposite ends to said strap, and a ball weight movable along said tube.

WILLIAM B. STEPHENSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,004,948 Irsch et a1 June 18, 1935 2,117,672 Linhard May 17, 1938 2,122,640 Field et a1. July 5, 1938 2,126,994 Hirsch et a1. Aug. 16, 1938 2,435,166 Stephenson June 2'7, 1948 FOREIGN PATENTS Number Country Date 363,400 Great Britain Acc. Dec. 16, 1931 

